This project investigates the problems associated with cardiopulmonary bypass and deep hypothermia in newborns. Current work is focused upon defining changes in platelets and platelet aggregation-disaggregation during bypass, and the effects of these changes on postbypass coagulation and bleeding. In addition, the effect of cardiopulmonary bypass upon the accumulation of extravascular lung water is being studied with both gravimetric and double indicator dilution techniques.